I can give you some encouragement about the exhausts. Today we flew our turbine powered Horten in windy conditions 24 - 28 mph. I shortened the exhausts back to scale position and it flew ok. However turns were not so easy especially into wind and needed drag rudders to haul the plane round, this was caused by the very windy conditions. I hope to post some video in the next few days.

I am sure that the instability found is a swirl issue with the fan units. Contra-rotating fans or fans with vanes should solve the problem but needs testing on the bench.

John

Images

Thanks John! Your Horten looks great. Are you using frise ailerons? I was pretty sure that the instability was caused by some sort of spiral slip-stream caused by the EDF units. The changesun 90mm units have some fairly long stators behind the actual fan, so I hope that these stabilize the airflow a bit.

That said, we do have intentions on doing a good bit of testing on the bench before flying these. The biggest issue we are having right now, is determining if and how much spiral airflow we have after the fan. The only way I can think of, is to tape some pieces of string to the TE of each stator and then run the fan to see what they do.
Any suggestions?

I attached a link of some test flight of Ralf's Ho229, the same construction of a Ho-229 V3 John, Ralf and I am flying. Our Ho-229 has an wing span of 3336 mm = 132 inch, ralf and me, we are using 2 off 120 mm EDF, John 2 jet turbine.
We tried to find out if there are some turbulence at the tail section during flight.

The EDF-versions NEEEEEED some helpers like tube extensions!
Or thrust vectoring in combination with a small fin under the tail section, like Uwe Heuer is using at his Ho-229.

Don't spoil your nice Ho-229 by cutting down the tube extension, the desaster will come by surprise, you will not notice any difficulties before!

Heiner,
Input from guys like you all that have experience is exactly what we were hoping for!

I hadnt though of the drag from the frise stule hinging when using as an elevator. Since we have plans to use the flaps as the inboards down and outboards up, i can setup the mix to use the outboard flaps as helper elevators as well.

The original Ho-229 V3 had 3 flaps at each wing. As ailerons you have to use the outer flaps, they work perfect as friese style flaps. But then you have to use the inner flaps as elevators.

To use all 3 flaps during landing procedure makes it a little complicate. Because, when you lower some flap as a drag rudder, you have to lift some other rudder to keep the nose down or the Ho-229 in level flight. Still you need some movement left at the aileron to correct the direction of your flight.

The most important thing you have to think about, the front wheel leg must be adjustable.
During take off you need an angle of attack of about 6-8 degree, during landing an angle of attack of 0 degree.

Heiner,
Thanks again for the input. I believe i have seen John's ingenious way of the adjustable nose strut. If its the one i am thinking of, it involves a pin in the nose strut that is extracted when the gear is put down and allows the compression spring to slide further up the strut, which lowers the Angle of attack on landing. Is this correct?

If so... now I just need to find someone to build 2 sets of nose struts. any takers?

I started with an adjustable nose strut, as it seemed it was necessary. However we have found that by making good use of the flaps and landing gear to slow the plane down it is possible to land on the 3 wheels together with a 7 degree up angle. It is impossible if you do not use flaps. I now lock the nose leg in its takeoff position.

The positive angle for takeoff is needed because the rear wheels are a long way back from the C of G and it cannot rotate like most modern planes. It just flies off all 3 wheels together with full up elevator held until it is airborne.

Clearly if you come in at too flat an angle with a long nose leg the plane will bouce and wheelbarrow on the nose wheel with unpredictable results!

We never deploy retracts until over the threshold and as soon as retracts are down we lower the flaps.